Physical enrichment for improving welfare in fish aquaculture and fitness of stocking fish: A review of fundamentals, mechanisms and applications

Problems and solutions for hatchery release: a framework

“…Projects based on this principle are often called environmental enrichment (Arechavala-Lopez et al, 2022). Most evidence shows that environmental enrichment can significantly improve the adaptive behaviors of hatchery fish by enhancing responses to behavioral and physiological stress as well as neural development and neurogenesis, although the mechanisms are not fully understood (Näslund and Johnsson, 2016;Zhang et al, 2022;Zhang et al, 2023a;Zhang et al, 2023b). More importantly, environmental enrichment can improve the learning ability of fish (Zhang et al, 2022).…”

“…A recent meta-analysis showed that introducing physical structures alone could not significantly improve fish survival rate, suggesting that the desired effect of environmental enrichment depends on whether the introduced cues match the target fish species, including the type, intensity, and duration of enrichment (Zhang et al, 2022). For examples, bottombased structures (such as cobbles) are more suitable for demersal fish, longer duration of enrichment may be needed for species featuring greater longevity (such as Atlantic salmon vs. zebrafish), and fishes whose natural habitats have complex water flow fields (such as rocky fishes) may benefit from flow exercise (Arechavala-Lopez et al, 2022;Zhang et al, 2023a). In this case, a preference test is an appropriate candidate to determine these factors (Näslund and Johnsson, 2016;Zhang et al, 2023a).…”

“…For examples, bottombased structures (such as cobbles) are more suitable for demersal fish, longer duration of enrichment may be needed for species featuring greater longevity (such as Atlantic salmon vs. zebrafish), and fishes whose natural habitats have complex water flow fields (such as rocky fishes) may benefit from flow exercise (Arechavala-Lopez et al, 2022;Zhang et al, 2023a). In this case, a preference test is an appropriate candidate to determine these factors (Näslund and Johnsson, 2016;Zhang et al, 2023a). Generally, conditioning strategies are still evaluated primarily at the behavioral level, and there are few long-term in-situ monitoring studies on their effects on fitness.…”